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The Web Open Font Format (WOFF) is a font format for use in web pages. It was developed during 2009[3] and is now a World Wide Web Consortium (W3C) Recommendation.[4]

Web Open Font Format
Filename extension
  • .woff
  • .woff2
Internet media type
  • font/woff
  • font/woff2
  • application/font-woff (deprecated)
Magic number
  • 77 4F 46 46 ("wOFF" in ASCII)
  • 77 4F 46 32 ("wOF2" in ASCII)
Developed by W3C
Type of format Font file
Container for SFNT fonts

WOFF is essentially OpenType or TrueType with compression and additional metadata. The goal is to support font distribution from a server to a client over a network with bandwidth constraints.


Submission as a standardEdit

The WOFF specification was written by Jonathan Kew, Tal Leming, and Erik van Blokland,[3] with reference conversion code written by Jonathan Kew.[5] Following the submission of WOFF by the Mozilla Foundation, Opera Software and Microsoft in April 2010,[6][7] the W3C commented that it expected WOFF soon to become the "single, interoperable [font] format" supported by all browsers.[8] The W3C published WOFF as a working draft in July,[9][10] and it became a W3C Recommendation in December that year.

WOFF 2.0, with reference code provided by Google,[11] is a proposed update to the existing WOFF 1.0 with improved compression and is currently being evaluated.[12] WOFF 2.0 uses Brotli as the byte-level compression format.


WOFF is essentially a wrapper that contains SFNT-based fonts (TrueType or OpenType) that have been compressed using a WOFF encoding tool to enable them to be embedded in a Web page.[3] The format uses zlib compression (specifically, the compress2 function),[3] typically resulting in a file size reduction from TTF of over 40%.[13] Like OpenType fonts, WOFF supports both PostScript and TrueType outlines for the glyphs.[14]

Vendor supportEdit

The format has received the backing of many of the main font foundries[15] and has been supported by all major browsers:

Some browsers enforce a same-origin policy, preventing WOFF fonts from being used across different domains. This restriction is part of the draft CSS 3 Fonts module,[26] where it applies to all font formats and can be overridden by the server providing the font.

Some servers may require the manual addition of WOFF's MIME type to serve the files correctly.[27] Since February 2017, the proper MIME type is font/woff for WOFF 1.0 and font/woff2 for WOFF 2.0[1][2]. Prior to February 2017, the standard MIME type for WOFF 1.0 was application/font-woff, and some applications may still use the old type, though it is now deprecated.[1]

WOFF 2.0, based on the Brotli compression algorithm and other improvements over WOFF 1.0 giving more than 30% reduction in file size, is supported in Chrome (since version 36),[28] Edge (since version 14),[29] Opera (since version 26),[30] Firefox (since version 35)[31] and Safari (since version 10).[32]

See alsoEdit


  1. ^ a b c "Media Types". IANA. 2017-10-12. Retrieved 2017-10-17. 
  2. ^ a b "The "font" Top-Level Media Type". IETF. February 2017. RFC 8081 . Retrieved 2017-10-17. 
  3. ^ a b c d Kew (Mozilla), Jonathan; Leming (Type Supply), Tal; van Blokland (LettError), Erik (2009-10-23), WOFF File Format (draft of 2009-10-23), Mozilla Foundation, retrieved 2010-01-30 
  4. ^ WOFF File Format 1.0
  5. ^ WOFF conversion reference code, retrieved May 8, 2016 
  6. ^ WOFF File Format 1.0 Submission Request to W3C
  7. ^ Galineau, Sylvain (2010-04-23), Meet WOFF, The Standard Web Font Format, Microsoft 
  8. ^ Team Comment on "WOFF File Format 1.0" Submission
  9. ^ WOFF - Now loading fonts on websites, The H, 2010-07-28 
  10. ^ Buckler, Craig (2010-08-17), W3C Backs the WOFF WebFont Standard, SitePoint 
  11. ^ Reference WOFF2 generation code, retrieved May 8, 2016 
  12. ^ W3C: WOFF 2.0 Evaluation Report
  13. ^ Stefanov, Stoyan (2009-10-20), @font-face gzipping - take II,, retrieved 2010-01-30 
  14. ^
  15. ^ Wardle, Tiffany (2009-07-16), Typegirl - Most of the important foundries are supporting #webfont, tumblr, retrieved 2010-02-05 
  16. ^ Shapiro, Melissa (2009-10-20), Mozilla Supports Web Open Font Format, Mozilla Foundation, retrieved 2010-02-05 
  17. ^ Colyer, Matt (2010-09-21), Typekit adds Chrome 6 WOFF support, Typekit 
  18. ^ Hachamovitch, Dean (2010-06-23), HTML5, Native: Third IE9 Platform Preview Available for Developers, Microsoft 
  19. ^ KDE SVN Revision 1088984, KDE Bugzilla, 2010-02-12, retrieved 2011-10-14 
  20. ^ A first glimpse at Opera 11.10 "Barracuda", Opera Software, 2011-02-17, retrieved 2011-02-17 
  21. ^ Web specifications support in Opera Presto 2.7, Opera 
  22. ^ Safari Features, Apple, 2011-06-06, retrieved 2011-10-14 
  23. ^ Safari 5.1 Changelog,, retrieved 2011-10-14 
  24. ^ Bug 38217 - [chromium] Add WOFF support, WebKit 
  25. ^ Bug 31302 - Add WOFF support for @font-face, WebKit 
  26. ^ CSS Fonts Module Level 3
  27. ^ "Webfonts are not loading in Firefox". Fontspring. Retrieved 2013-01-01. 
  28. ^ Chromium 36 Release Notes, Google 
  29. ^ Speed up page load with WOFF 2.0 fonts in Microsoft Edge, Microsoft 
  30. ^ Opera 26 Release Notes, Opera Software ASA 
  31. ^ Firefox 35 Release Notes, Mozilla Developer Network 
  32. ^ What's new in Safari, Apple 

External linksEdit